Waste heat boiler



PMs.

April 3 BQURNE WAS TE HEAT BOILER Filed Aug. 1, 1945 INVENTQR flown 0 3.50 U/PWE ATTORNEYE Patented Apr. 1, 1947 UNITED STATES PATENT OFFICE WASTE HEAT BOILER Roland B. Eourne, West Hartford, Conn assignor to The Maxim Silencer Company, Hartford, Comp, a corporation of Connecticut Application August 1, 1945, Serial No. 608,162

Claims. 1

The present invention relates to waste heat recovery silencers adapted for use on the exhausts from internal combustion engines and relates particularly to that type of device which is adapted to run dry when there is no steam demand.

In heat recovery silencers of this type, the water level in the boiler and therefore the amount of heat recovered is preferably automatically controlled as by the steam pressure in the boiler. The greater the demand for steam, the more water is introduced into the boiler, and vice versa.

Heretofore it has been proposed to provide a pipe connection at the bottom of the water jacket of the boiler through which water is drained from the boiler when the demand for steam decreases and through which water is fed to the boiler as the demand for steam increases. In cases where the boiler has been running dry for some length of time, the temperature of the entire structure approaches that of the exhaust gases. While these temperatures are not sulficiently high to cause a flash explosion upon the introduction of water to the boiler, nevertheless the sudden chilling of the lower portion of the water space may result in comparatively large strains particularly in the neighborhood of welded seams. in time cause the metal in or near such welded seams to crack.

The present invention is directed at preventing such thermal shock by the employment of a unique piping arrangement which does not alter the basic mode of operation of the device or its automatic control system.

The prime purpose of the invention is accomplished by providing a bottom outlet connection and a top inlet connection which are joined together through check valves to a common pipe leading to the automatic control valve, The check valves are directioned so that water flowing into the boiler enters the water jacket in its upper part and in such a. manner that the water is sprayed or otherwise directed against the internal walls of the jacket. Much of this water is turned to steam immediately and by the time any solid water reaches the bottom of the jacket the metal will have been sufficiently cooled as to greatly lessen 01 indeed prevent altogether any danger from thermal shock.

For a complete description of the device, reference is made to the drawings in which Fig. 1 shows a vertical section through a typical heat recovery silencer together with a dia Repeated thermal shocks may 2 gram of the piping and controls for a completely automatic installation;

Fig. 2 shows a, transverse section through the unit on line 2-2 of Fig. 1';

Fig. 3 is similar to Fig. 2 but shows a modified type of inlet connection; and

Fig. 4 is a detail section of the control valve.

Referring to Fig. 1, the general operation of the boiler and automatic control will be described only briefly since the invention herein disclosed pertains particularly to one feature only of the entire system. The boiler comprises a cylindrical shell I! having an inlet header l2, an outlet header [3, and an intermediate partition l4 dividing the interior of the device into a gas inlet chamber I5 and a gas outlet chamber I B. Exhaust gas from the engine enters the inlet chamber 15 through an inlet conduit [1 and. leaves the outlet chamber :6 through an outlet conduit 18. Positioned around the periphery of the shell II and passin through the intermediate header M are a plurality of angular members 19 continuously welded to the interior of the shell H and to each other to form a plurality of 'gas passages 20 extending from the inlet chamber I5 to the outlet chamberjlii. The angle members 1'9 not only form the gas passages 20 but also act as extended heating surfaces for the shell ll, greatly increasing the efiiciency of the heat transfer.

Outside the shell II is a shell 2!, which, together with an annular extension 22 of the" inlet header [2 and an expansion ring 23, forms a water and steam space 2 1. A pump control switch 25 of common type shuts down the motor 26 of the circulating pump 21 when the water level in the space 2'4 reaches a predetermined level. Steam from the boiler passes to the heating or other load through the main steam pipe 28' and returns to an accumulator tank 29 through the return line 353. Make-up water is fed to the tank 29 through the line 3|, controlled by a fioatvalve 32 in the usual manner. The tank 29 is equipped with a vent 33,

The heart of the automatic control features of the system is the three-way, pressure operated valve 34, actuated by steam pressure in the space 24 through the small steam pressure line 35 which communicates with the top of the steam space 24. Near the top of the space 24 is positioned a water inlet connection 35 and near the bottom of said space is positioned a water outlet connection 3'5. Check valves 38, 39, with arrows indicating the direction of flow therethrough, are positioned in the feed Water line 48 and the water In Fig. 3 is shown a simple spray head 5t. cases where the exhaust gas temperature is of return or drain line 4| respectively. These two lines are joined together as shown into a pipe 42 which is connected to the valve 34. The valve 34 is further connected to the outlet of the circulating pump 21 through a pipe 43 which is, in turn, connected to the tank 29 through a relief valve 44. The third connection of the valve 34 leads to the bottom of the tank 29 and a submerged heater 45, through the pipe 46.

The system operates in the following manner.

The amount of steam generated, other things being equal, is dependent upon the amount of water in the boiler since the water level determines the amount of heating surface involved in extracting heat from the exhaust gases. When the system demands less steam, the pressure in boiler through the valve 34 and the water inlet pipe 40, through the check valve 38 and into the boiler at the inlet connection 36.

I It will be seen that should the boiler be running' dry for any length of time, the temperature 'of the boiler will attain practically the temperature of the exhaust gases while the water in the tank 29 will, be relatively cool. Upon a demand for steam, this water will be pumped into the relatively hot boiler and it is one purpose of this invention to introduce this water at a point remote from any important welds such as those connecting the annular plate 22 to the shells H and 2|, as hereinbefore described.

The water may be safely introduced through the top inlet connection 36 through an internally disposed spray arrangement. In Fig. 2, is shown a circumferentially extending spray pipe 4'5 closed at its ends and fitted with a number of small spray orifices 48 whereby the incoming water is sprayed over a considerable area of the surfaces "of, the shellsfll and 2|, thus greatly reducing the tendency for any thermal'shock to the welds. The shell seam welds are preferably positioned at a' point remote from the spray pipe 4?, as at 49. In

ing or lowering the water level in said boiler, one.

branch of said feed pipe being connected to the walls of the water space.

water compartment of said boiler at a point remote from the bottom thereof, a check valve in said first branch set to permit the passage of water to the boiler only; a second branch of said drain pipe being connected to the water compartment of said boiler at a point at or near the bottom thereof, a check valve in said second branch set to permit water to drain from the boiler; a drain, a source of water under pressure, and valve means to connect the feed and drain pipe alter- V natively to said source or to the drain.

2. In a steam boiler adapted to be run dry, a source of water under pressure, a sump. a dram pipe connected to the lower part of the boiler and containing a check valve permitting flow out of the boiler only, a feed pipe connected to the upper part of the boiler and containing a check valve permitting flow into the boiler only, a common connection between the drain and feed pipes, and valve means to couple said common connection alternatively to the source or to the sump.

3. In a steam boiler adapted to be run dry, a source of water under pressure, a sump, a drain pipe connected to the lower part of the boiler and containing a check valve permitting flow out of the boiler only, a feed pipe connected to the upper part of the boiler and containing a check valve permitting flow into the boiler only, a common connection between the drain and feed pipes, and valve means responsive to pressure in the boiler to couple said common connection to the sump upon an increase in said pressure and to the source upon a decrease in said pressure.

l. In a steam boiler adapted to be run dry, a combined bnanched feed and drain pipe for raisng or lowering the water level in said boiler, one branch of said feed pipe being connected to the water compartment of said boiler at a point remote from the bottom thereof, a check valve in said first branch to permitth'e passage of water to the boiler only; a second branch of said drain pipe being connected to the Water compartment 1 of said boiler at a point at or near the bottom thereof, and a check valve in said second branch to'permit water to drain from the boiler; a drain, a source of water under pressure, and valve means to connect the feed and drain pipe alternatively to said source or to the drain, said feed pipe opening into the upper part of the boiler in one or more nozzles directing entering water against the 5. In a steam boiler adapted to be run dry, a

source of water under pressure, a sump, a drain pipe connected to the lower part of the boiler and containing a check valve permitting flow out of valve means to couple said common connection alternatively to the source or to the sump, said feed pipe opening into the upper part of the boiler in one or more nozzles directing entering water against the walls of the water space.

ROLAND B. BOURNE. 

